An addition manufacturing technique is a technique for obtaining a desired three-dimensional molded product in the following manner. According to this technique, a thermoplastic resin, a photocurable resin, a powdered resin, a powdered metal, or the like is fused and cured based on three-dimensional shape data by melt extrusion, inkjet, laser light, an electron beam, or the like, and is laminated in a thin film form. A molded product is obtained directly from the shape data, and a complicated shape such as a hollow shape or a meshed shape can be integrally molded. Therefore, a field of application has been expanded to medical and aircraft industries, an industrial robot, and the like in addition to creation of a small lot or custom made test model.
In order to obtain a three-dimensional molded product, a three-dimensional molding apparatus generally called a 3D printer is used. Specifically, an inkjet ultraviolet curing type 3D printer using an acrylic photocurable ink, a heat melting lamination type 3D printer using an acrylonitrile-butadiene-styrene resin, a polycarbonate resin, a polyphenylsulfone resin, a polyetherimide resin, or the like, a powder molding type 3D printer, an optical molding type 3D printer, and the like are known. Examples of the inkjet ultraviolet curing type 3D printer include Objet manufactured by Stratasys Ltd. and AGLISTA manufactured by Keyence Corporation. Examples of the melting lamination type 3D printer include FORTUS, Dimension, and uPrint manufactured by Stratasys Ltd. Examples of the powder molding type 3D printer include SLS manufactured by 3D Systems, Inc. Examples of the optical molding type 3D printer include SLA manufactured by 3D Systems, Inc. and DigitalWax manufactured by DWS Corporation.
According to three-dimensional molding, a three-dimensional molded product having a complicated shape can be formed. However, in order to manufacture a hollow structure or the like, it is necessary to dispose a shape supporting structure for temporarily supporting a resin during molding at a bottom of a three-dimensional molded product in order to prevent the three-dimensional molded product from being deformed by its own weight. In a case of the powder molding type 3D printer in which a powder raw material is bonded or fused, an unbonded or unfused powder acts as a support and supports a structure. Therefore, a three-dimensional molded product can be obtained by scraping off an excess powder after manufacturing. Even in the optical molding type 3D printer in which a photosensitive resin is gradually cured by laser light or the like, an uncured photosensitive resin supports a structure. Therefore, a support can be removed only by pulling up a three-dimensional molded product from a photosensitive resin tank. On the other hand, when widely used melt extrusion type or inkjet type three-dimensional molding is performed, a three-dimensional molded product made of a model material and a support made of a support material are formed simultaneously. Therefore, it is necessary to provide a step of removing the support material after formation.
However, removing a support material after molding is not easy work at all. The support material is fused, adheres, or sticks to an intended three-dimensional molded product. Therefore, in work of peeling the support material from the molded product, a means such as peeling the support material manually using a spatula, a brush, or the like, or blowing off the support material with a water jet is usually used. However, there is a risk of breakage of the three-dimensional molded product. Therefore, necessity of careful work has been a large burden.
Therefore, as the support material, a thermoplastic resin, a hot melt wax, a material which can be dissolved in water or an organic solvent, a water-swellable gel, or the like is used. A separation method utilizing heating, dissolution, a chemical reaction, power washing such as hydraulic washing, electromagnetic wave irradiation, a thermal expansion difference, or the like according to a property of a support material has been proposed (Patent Literatures 1 and 2). Specifically, use of a resin which can be easily peeled from a model material (Patent Literatures 3 and 4), melt-removing a support material by heat using a wax as the support material (Patent Literature 5), a means for dissolving or dispersing a support material in an alkali, water, or an organic solvent (Patent Literatures 6 to 11), and a means for removing a support material using an electrolyte solution such as tetramethylammonium hydroxide as a washing liquid under stirring or energizing (Patent Literature 12) have been proposed.
However, also in these support materials, it is extremely difficult to efficiently remove a portion with which details are clogged. In addition, when a method for melt-removing a wax or the like by heat is used, an oily residue adheres to a surface of a three-dimensional molded product after removal. Therefore, finishing work for the three-dimensional molded product such as wiping is required. Furthermore, a wax penetrates into the model material by heating. As a result, a surface state of the three-dimensional molded product is deteriorated disadvantageously.
Also, even when a supporting material is dissolved or dispersed in an alkali, water, or an organic solvent, the dissolved or dispersed support material is not separated from a washing liquid. Therefore, the support material easily adheres to a three-dimensional molded product immersed in a washing tank. As a result, surface contamination of the three-dimensional molded product is brought about. As a result, finishing work for the three-dimensional molded product, such as surface wiping is required.
On the other hand, in a method for removing a resin from a substrate by swelling in a washing liquid such as an organic solvent, a peeled resin and the solvent are separated into two phases. Therefore, a surface of the substrate is hardly contaminated, and peeling from a fine structure is easy. Therefore, this method is well known as a means used for removal of a photoresist in semiconductor manufacturing (Patent Literature 11). However, it is usually necessary to apply an external force such as ultrasonic vibration or flow of a washing liquid after swelling for peeling a photoresist material. Therefore, it is a disadvantage that an increase in cost and reduction in a production efficiency are caused by installing a special and large-sized washing apparatus, adding a peeling step, and the like
Therefore, development of a support material requiring no manual removal, finishing step, or special large-sized washing apparatus, and development of an efficient method for manufacturing a three-dimensional molded product using the same have been desired.